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Computational simulation of the compression test of the open cell metal foam
Homola, Václav ; Skalka, Petr (referee) ; Ševeček, Oldřich (advisor)
The thesis presents computational simulation of compression test of a nickel foam and the 3D reconstruction of micro-CT images was utilized to generate the foam’s model of geometry. Explicit FEM is used to simulate compression test using software tool LS-DYNA and the stress–deformation curve is obtained together with deformed model’s mesh used for subsequent analysis. Sensitivity analyses were performed to configure the model and ensure best fit with values obtained during real-life experiment. The ANSYS Classic environment was then used to simulate tensile test of the foam compressed to various thicknesses. The tensile moduli in three mutually perpendicular directions of nickel foam were computed and the results were compared to experimental values as well. The results of tensile test simulation revealed considerable anisotropy of the foam’s elastic behavior. It can be said that the measured experimental data correspond very well with the elastic properties obtained from simulation up to certain level of compression. Analysis of the relationship between the element size and tensile moduli showed a significant difference between fine and coarse mesh. The optimal level of discretization and the overall model configuration ensuring high level of accuracy is proposed in this thesis.
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Optimization of modal properties of the body in the air flow
Matějka, Jan ; Švancara, Pavel (referee) ; Skalka, Petr (advisor)
The bachelor thesis deals with dynamic analysis of the rod body, which is excited by the Karmán vortices. In this thesis a method of countermeasure is also verified, which could be possibly used in order to supress the state of resonance in the body and which could minimalize the influence of the Karmán vortices on the structure. This method consists in change of the mass in specific parts of the body in order to change modal properties of this body. The main goal of the thesis is to find suitable configurations of the mass distribution depending on air flow velocity for purpose of minimalization the influence of the Karmán vortices on the construction. This is achieved by optimization of modal properties. The optimization is based on results of harmonic analysis and is considering possibility of practical use.
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Numerical simulation of failure of ceramic foams upon mechanical loading
Hanák, Jiří ; Skalka, Petr (referee) ; Ševeček, Oldřich (advisor)
The master’s thesis deals with a numerical simulation of failure of ceramic foams with open-cell structure and with understanding of conditions required for the failure of the structure under various mechanical loading conditions. To this purpose, the so-called stress-energy coupled criterion was utilized. The motivation for this thesis was to create a model able of the most accurate prediction of the ceramic foam strength in comparison with experimental observations. First part of the thesis is focused on the theoretical background required for solving the problem. More specifically there are mentioned methods of the foam material modelling, Linear Elastic Fracture Mechanic (LEFM) and coupled stress-energy criterion used for definition of the crack initiation. In the second part of the thesis, numerical Finite Element Analyses (FEA) whose main purpose was to determine critical conditions necessary for the initiation of strut failure within the foam structure, were performed. These pieces of knowledge were then used for creation of the numerical simulation algorithm of the mechanical test of foam material with regular cell pattern. Outputs of numerical simulations were at the end of this work compared with experimental results (of the compression test) made on the real Al_2 O_3 foams prepared by 3D printing technology and provided by the Institute of Physics of Materials Czech Academy of Science. It can be concluded that a good agreement between results of both approaches was reached and the prediction of the ceramic foam mechanical strength using the developed model is in the meanwhile the most accurate estimation from recently published approaches.
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Finite element simulation of stresses in plasma-sprayed thermal barrier coating
Lacina, Zdeněk ; Slámečka, Karel (referee) ; Skalka, Petr (advisor)
Bachelor‘s thesis focuses on the study of stress states in thermal barrier coatings. A two-dimensional computational model of thermal barrier coating was created using ANSYS software, on which the process of cooling of thermal barrier from working temperature to room temperature was simulated .The stress distribution in ceramic layer was studied then. The output of this thesis is a description of the influence of roughness, amplitude and TGO layer on the stresses in a ceramic layer of thermal barrier. Matlab software was used to process the results.
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Napjatostně deformační analýza mostu v Třineckých železárnách
Ščerba, Bořek ; Skalka, Petr (referee) ; Fuis, Vladimír (advisor)
The bachelor thesis analyses stress and deformation of the truss construction. The first point of the thesis is a research, which includes obtaining information about the construction, for exemple dimensions, loads, purpose, history etc. Then, calculation models are created considering a different level of simplification. Two analytical models are crutial for the thesis – one statically determinate and the other statically indeterminate. They are used for analysing two different loads applied to the construction using methods of solid mechanics – it’s own weight and its own weight in combination with a weight of a vehicle that is driving through. Afterwards, the statically inderteminate model is verified using finite element method (FEM).
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Comparison of mechanical properties of bolts with various surface treatment and upon consideration of their operation on the safety limit
Krško, Peter ; Skalka, Petr (referee) ; Ševeček, Oldřich (advisor)
This bachelor thesis deals with issues of critical bolt joints tightening on the safety limit. The aim of this work is to find the optimal surface treatment of the bolt for reliable application in industrial vacuum pumps and to clarify its stress-strain behaviour upon using various surface treatments and different surface lubrication. Next part consists of finding the maximum torque values causing a fracture in bolts of the vacuum pumps. For this purpose, on one hand, the analytical model of the bolt joint is used and, on the other hand, the experimental observations on the real bolt joint are utilized. The outputs of both approaches are then compared to each other and, on their basis, the most suitable surface treatment of the bolt joint for the given industrial pump is recommended in order to achieve the maximum possible safety against torque applied to the bolt when assembling the device.
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Napjatostně deformační analýza rozhledny Hraniční vrch
Novák, Tomáš ; Skalka, Petr (referee) ; Fuis, Vladimír (advisor)
Bachelor thesis is focused on stress and deformation analysis of strut frame, which is based on lookout tower Hraniční vrch by the city Město Albrechtice. The main goal is to create simplified 3D model and his resulting analysis at various degree of static indeterminateness. The first part contains introduction to history of lookout tower, theoretical introduction to bar, strut frame and limit state, followed by calculation of three various static indeterminate level. In the last part is verification of analytic results by numeric method. Another goal is to create thesis, which will also give a guidence for future solver of more complex 3D strut frame.
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Determination of mechanical properties of open ceramic foam structure using finite element method
Barančík, Milan ; Navrátil, Petr (referee) ; Skalka, Petr (advisor)
The thesis is concerned with creating of a computational model of open-cell ceramic foam and determining mechanical properties of open-cell ceramic foam using computational modeling. The geometry of Kelvin cell was used for creating the model of geometry of the foam. The model of geometry of ceramic foam structure was meshed with solid elements, with beam elements and with combination of rigid beam and beam elements. Elastic properties of the foam were determined by two types of mechanical loading. Young´s modulus and Poisson´s ratio were determined by tensile/compressive mechanical loading and shear modulus was determined by shear mechanical loading. The relationship between mechanical properties of the foam and the ratio of diameter of strut D and length of strut L was analysed in the thesis. A good agreement was found out between Young´s modulus determined by solid element based and Young´s modulus determined by modified beam based model of geometry of the foam structure – for ratio D/L up to 0,6. In the case of Poisson´s ratio a good agreement was determined up to D/L = 0,4. In conclusion the value of Young´s modulus 1,97 GPa which was determined by computational modeling was compared with the value 1,56 GPa which was determined experimentally on ceramic foam. This difference was caused by idealization of geometry of the real ceramic foam material. In addition, mechanical properties of the ceramic foam material are influenced by structural imperfections of the material.
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Three-point bending test of foam laminates
Kelecsényi, Matej ; Navrátil, Petr (referee) ; Skalka, Petr (advisor)
The bachelor thesis deals with the formation and the spread of disorder of crossbeams in core of composite, in ceramic foam with homogeneous structure formed by Kelvin cells with open porosity loaded by three-point bending test. The method of finite element in software ANSYS was used for the creation of composite sample calculation model as well as in calculation of sample loads. The results of the thesis are the values of the sample reaction force and of the first main tension on crossbeams of foam core sample obtained by loading of the foam composite sample. The area of breaches crossbeams was inferred from the analysis of composite core structure breach. In conclusion were evaluated the results obtained in this thesis.
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Sheet thickness optimization of the bolted steel tank
Konečný, Jiří ; Lyčka, Petr (referee) ; Skalka, Petr (advisor)
This thesis deals with bolted steel tanks, especially modification one of them. This modification is realized in cooperation with Kohimex spol. s r.o., which is assembling theese tanks for many years. The thesis continues on the bachelor one called "ASSEMBLED STEEL TANKS", which has already dealt with this issue. At the beginning of the thesis the issue of tanks is explained. Furthermore, there is made description of the tank modification details. At the next stage, the work presents stress-strain states of the tank, first for the current tank and then for the modified option. On the basis of completed analysis is made economic evaluation of design modified tank option due to the current tank. The results of this study allow better issue understanding of bolted tanks designing or they give impuls to improve the current way of designing.
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